The present invention relates to injection molding apparatus, and more specifically to an improved machine design and system for the efficient performance of the injection molding process.
Injection molding machines are well known, and generally include two major sub-assemblies or systems; namely, the injection system for handling, heating and injection of the liquid thermoplastic resin into the mold cavity under extremely high pressure, and the system for handling the mold components. The latter system normally includes an arrangement for pre-loading the mold components in clamped relation and some form of ejector means for removing the molded parts from the mold cavity. As can be appreciated the larger and more complex the parts to be molded, the greater the injection and clamping pressure required to achieve properly molded parts. Thus, one purchasing an injection molding machine normally will have to purchase a unit of sufficient size and capacity to handle the maximum molding job envisioned. As such, most molding machines are "over-sized" with respect to a vast majority of their every day uses. Also, these prior art types of machines are of the self-contained integrated variety, in that each machine includes its own hydraulic fluid pressurizing system, and in many instances its own air compressing system. As a result of the necessity of purchasing "over-sized" machines, considerable cost is expended in obtaining machine capacity which is unnecessary, and is rarely used. However, the presence of integrated self-contained systems, requires operation during every day use, resulting in a waste of energy and serving to increase manufacturing cost.
The present invention is directed primarily at an individual machine design which was developed for incorporation in an overall system utilizing a number of machines and central sources of supply for the operating requirements such as cooling water, compressed air and high pressure hydraulic fluid, so as to eliminate redundant, integrated systems as a result thereof. The present invention minimizes the cost of machine operation as well as the initial cost of the machine.
Concerning the basic overall system there is provided a plurality of machines each of which has been designed and fabricated without the employment of an integrated, individual system for high pressure hydraulic fluid or compressed air although the machines are designed to operate utilizing compressed air and pressurized hydraulic fluid. As a further matter these machines will require additional operation requirements, such as cooling water and electrical power. In this regard, a single, centrally located source for each operating necessity is provided at a first, relatively remote location. This location is accoustically and environmentally isolated from the area where the individual machines are located, with the operating mecessities or requirements, viz., compressed air, high pressure hydraulic fluid, cooling water, and electric power, being supplied to the machines by service lines and a manifold system which controls and allocates a particular operating component to a selected machine based upon its requirements, as determined by the job being performed. As such, the machines can be operated at varying levels or capacities, without overloading the system, and also without wasting the particular operating component involved, be it cooling water, compressed air, power or high pressure hydraulic fluid.
Further, the overall machine of the design of the present invention is adapted for improved operation. In this regard, a "unit mold" concept is utilized, similar to that as disclosed in the Inventor's prior U.S. Pat. No. 3,737,268. The unit mold concept is employed in conjunction with a novel clamping mechanism for attaining the pre-loading of the abutting mold components while utilizing an extremely short stroke for the moveable mold platen, which results in the provision of shorter tie-rods. This is accomplished without compromising the overall rating of the machine as to the mold injection pressure that can be employed. In this regard, it should be kept in mind that most prior art machines utilize a toggle type of arrangement for producing the initial loading of the mold components, and as such of necessity employ relatively long tie-rods and a lengthy stroke in moving the mold component rearward from the molding position to the unloading or ejecting position.
Accordingly, it is an object of the present invention to provide a new and novel system for accommodating a plurality of injection molding machines wherein said machines are supplied with required operating components from a centralized source, the source for said operating components being acoustically and environmentally isolated from the area of machine operation.
A further object of the invention is to provide an improved machine design for use in a system of the type described above.
In accordance with the above objects, there is provided a machine which utilizes the basic sub-assemblies of a standard molding machine, namely, heating and injecting means for the thermoplastic material, and a mold handling system for moving the mold components between a mold closed position and a mold open position. The mold handling system of this machine is improved to provide novel clamping and locking means which enable the desired clamping pressures to be attained without excessive mold travel and in a more uniform and reliable fashion. More specifically, the design employs a pair of mold platens, each of which is recessed to receive a mold insert or component having a portion of the mold cavity formed therein. The mold platens are integral parts of the machine, with one being larger than the other, the larger of the two platens containing the ejection mechanism and being fixedly mounted with respect to the machine base and the tie-rods extending longitudinally of the machine base. The other platen is of lesser size and is slidably mounted on the tie-rods for movement into abutting relation with the stationary platen to define the mold closed position, and away from said stationary platen to define the mold open position. The initial travel or movement of the second platen is effected with a high-speed, low-pressure system which can rapidly traverse the movable platen to and from the desired operating positions. The moveable platen includes novel means for locking the mold halves in relative abutting position and for pre-loading the platens and the mold inserts prior to the high pressure injection of the heated thermplastic resin material. To achieve pre-loading, the moveable platen member includes two separate relatively moveable plate members with a high-pressure diaphragm interposed therebetween. The rearward plate member is adapted to be locked in position with respect to the machine tie-rods, and the diaphragm then pressurized to force the adjacent, forward plate member towards the stationary mold platen under high-pressure to achieve the desired pre-loading. The design is extremely advantageous, as the force from the high pressure diaphragm is applied equally over a relatively large area and permits achievement of the necessary pre-loading rapidly and without the localized application of force, as is attendant with the prior art type of toggle pre-loading systems.
The above discussed specific objects and other objects will become apparent from the detailed description of the invention which follows, said description being setforth in conjunction with the accompanying drawings.